Temperature controlled surface wave feeder lines

ABSTRACT

The invention consists of a surface wave antenna feeder in the form of a conductive tubing coated with a dielectric to produce on the outside of the coated conductor a field carrying substantially the entire electromagnetic wave energy from the transmitter to the antenna, and providing inside the tubing a circulating fluid so controlled as to maintain the line at a constant temperature substantially to exclude longitudinal expansion, regardless of the power level of the surface wave and the temperatures surrounding the line.

United States Patent [72] Inventor Theodore lhfner 1501 Broadway, NewYork, N.Y. 10036 [21 I Appl. No, 830,932 [22] Filed June 4, 1969 I45]Patented Sept. 7, I971 [54] TEMPERATURE CONTROLLED SURFACE WAVE FEEDERLINES 7 Claims, 7 Drawing Figs.

[52] US. Cl 333/95 S, 333/97, 174/15 C [51] Int. Cl 1101p 3/08, H0lp1/30, 1101b 7/34 [50] Field ofSeareh 333/95 S, 95; 343/785, 704, 704.5;174/15 C, 47, 83; 138/ 155 [56] References Cited UNITED STATES PATENTS1,917,205 7/1933 l-lorle 343/704 2,031,975 2/1936 Northrup. 174/15 (C)2,867,778 1/1959 Hafner 333/95 (S) 2,946,970 7/1960 Hafner 333/95 (S)2,947,841 8/1960 Pickles et al 343/704 X 3,106,600 10/1963 Crosby 174/15(C) 3,187,279 6/1965 Hafner 333/95 3,201,724 8/1965 I-Iafner 333/95 (S)3,372,352 3/1958 Krank et a1. 333/95 (A) FOREIGN PATENTS 1,115,0974/1956 France 333/31 (A) 717,128 10/1954 Great Britain 138/155 OTHERREFERENCES Kimbark, E. W., Electrical Transmission of Power & Signals,John Wiley & Sons, 1949 pp. 58- 60 Primary Examiner-Herman Karl SaalbachAssistant ExaminerWm. H. Punter Attorney-Theodore Hafner ABSTRACT: Theinvention consists of a surface wave antenna feeder in the form of aconductive tubing coated with a dielectric to produce on the outside ofthe coated conductor a field carrying substantially the entireelectromagnetic wave energy from the transmitter to the antenna, andproviding inside the tubing a circulating fluid so controlled as tomaintain the line at a constant temperature substantially to exclude1ongitudinal expansion, regardless of the power level of the surfacewave and the temperatures surrounding the line.

PATENTEDSEP nan INVENT OR THEODORE HAFNER PATENTEDSEP'HSYI I 3, 03,904

' SHEEIZUFS FIG. 2.

1.8 32 FIG. 6.

IN VENTOR THEODORE HAFNER PATENTEDSEP 7am SHEEI 3 OF 3 ss-- v" INVENTORTHEODORE HAFNER s m g w wi aa I, I? "0 I t TEMPERATURE CONTROLLEDSURFACE WAVE FEEDER LINES The invention consists of an antenna feederline in the form of a conductive tubing coated with a dielectric andforming a surface wave transmission line, with means being applied tothe tubing either in the form of a coolant fluid or in the form ofelectric current so as to control the temperature of the line to make itsubstantially independent from atmospheric conditions while carryinghigh RF power, especially in the VHF and UHF frequency ranges.

One of the objects of the invention is to dispense with large coaxialcables and waveguides as antenna feeder lines to carry the high powerrequired for present day VHF and UHF television transmitters. Suchcables and waveguides are not only expensive in manufacture but theyalso involve very high cost of installation and maintenance. At the sametime of course, power must be carried over the feeder line with a verylow loss and an equally low VSWR; for example, at 50 kw. and 800 MHz., a500 ft. feeder line is expected to have a total loss of the order 0.7db. and VSWR over a bandwidth of MHz. of only 1.05.

In accordance with one aspect of the invention, an antenna feeder linein the form of a conductive tubing consisting for example of copper orcopperplate stainless steel, and coated with a dielectric of low lossfor example a loss figure of 0.0005 at UHF and forming a surface wavetransmission line, and capable of being arranged at a slant dependingfrom the antenna tower, is provided with a coolant system in which afluid is passed through the tubing maintaining its temperature constantand thereby reducing atmospheric influences to a minimum. At the sametime while providing loss and VSWR values equivalent to those of coaxialcable, for example of the rigid 6b-inch type, or of correspondingwaveguides, cost of manufacture and especially cost of installation ofthe feeder line are reduced to a fraction of those prevailing in thepast.

In a modification of the invention, instead of a fluid, electricalheating is applied to the tubing, to prevent icing, under control oftemperature difference prevailing between the temperature due to thepower carried by the line, or the absence of such power, and thetemperature caused by the weather.

These and other features of the invention will be more fully apparentfrom the drawings annexed herein to which:

FIG. 1 illustrates schematically an antenna feeder line in accordancewith the invention supported on an antenna tower; FIG. 2 a modificationthereof.

FIG. 3 shows an example of a tubular feeder line, in part only and in across-sectional side view; FIG. 4 a modification thereof.

FIG. 5 shows an example of the launcher arrangement for the feeder line,embodying certain principles of the invention, and

FIGS. 6 and 7 show parts of FIG. 5, for a UHF transmitter, in greaterdetail, also embodying certain aspects of the invention.

As apparent from FIG. 1, a tubular surface wave transmission line aswill be described in greater detail further below, and schematicallyindicated by line 1, is shown suspended from a tower part of which isindicated at 2, and which is 500 ft. high. Line 1 extends at a slant toa transmitter station 3 disposed about 100 ft. away from the foot oftower 2. Preferably the slant is so disposed as to permit line Idepending from tower 2 with minimum tension, say of the order of 2000lbs. for a 50 kw. 800 MHz. TV transmitter feeder line. Such a slant doesnot only reduce strain on the tower to a minimum but it also permits toreduce to a minimum any interference between the structure of tower 2and the field radius of surface wave transmission line 1, which isgenerally of the order of about I wavelength of the operative frequencyrange of the system.

Tubular line 1 is connected in a manner, at least in principle known perse, and as will be explained more specifically further below, to itsterminal equipment, at one end over a receiver horn 4 to an antennaschematically shown at 5; at its other end, line 1 is rigidly connectedover a similar launcher horn 6 and a coaxial cable 7 to the transmitterstation 3. Tubular transmission line 1 after having passed through thelauncher 6, is anchored to ground and also electrically grounded asindicated at 8, as need not to be explained in detail, and as may beconsidered well known per se for example, from US. Pat. SpecificationNo. 3,440,576.

At ground platform 8, another tube 9 is connected which leads a coolantfluid derived from a pump system schematically indicated at 10 butotherwise well known per se, into, and up to the tubular transmissionline I, on the top of which it is passed in a manner similar to thatdescribed above, through receiver horn 4 a tube portion 11 to a pipe 12attached to tower 2 for recirculation, and if necessary after recoolingor reheating as the case may be, in accordance with the temperaturerequirements of the system, or any other conditions of control.

In the specific embodiment of the invention shown in FIG. 1,recirculation pipe 12, is connected to another pump system schematicallyindicated at 13 and which is adapted to act as a heating system whilepump system 10 is adapted to act as a cooling system. Each of systems 10and 13 is controlled by the average temperature along tubular line 1 asindicated in FIG. 1 by control lines 14, 15 connected respectively tothermoelements (not shown) attached to the end portions 8, 11 of line 1,respectively which represent ground and top platform planes,respectively. Under control of these temperatures, or an averagethereof, the corresponding signal voltages, after amplification ifnecessary, well known in the art of telecontrol and telemetering, may beused to operate, depending on the temperatures involved, either pumpsystem 10 which cools the fluid passing therethrough, or pump systemwhich heats the fluid passing therethrough. In this way, tubular line 1may be maintained, regardless of its mode of operation or atmospheric orweather conditions, on a substantially constant temperature, which maybe relatively low or so determined as to produce optimum transmissionconditions and a minimum of mechanical stress such as extensions oflength due to varying temperature arising out of changes in thetransmitted power, atmospheric variations or other varying conditions.

Since fluid coolant or heating systems are well known per se, there isno need to describe such systems in greater detail; any type of suchsystem may be applied therefore, without departing from the scope ofthis disclosure.

In this particular application, the intention has the advantage that itwill not be necessary in the mechanical support of tubular line 1, toprovide means to compensate or tolerate longitudinal changes of line 1.All that will be necessary, is to provide the angular or rotary movementof the line under wind pressure, as will be explained further below inconnection with the attachment or guidance of the tubular line throughthe launching horn.

In the modification shown in FIG. 2, tubular line l-which is otherwisesuspended in a manner similar to that shown in FIG. 1 except certainchanges as conditioned by this modification-at an outer lower portion 16is electrically connected over line 17 to an AC or DC power sourceschematically indicated at 18, and over line 17' to an upper cableportion (not shown). Temperature sensor lines schematically indicated inFIG. 2 at l9, 19, after comparing temperatures prevailing on line 1, oraveraged from its ends, with atmospheric temperatures, control powersource 18 which applies low frequency or DC current to tubular line 1,thereby increasing its temperature to an amount preventing the formationof ice or providing other conditions maintaining maximum efficiency.

Since such heating systems and their control under varying temperatures,are well known per se, they will not be described in detail, and theymay be applied in any form or manner whatsoever without limiting thescope of this invention.

FIG. 3 shows a portion of the tubular line, and more specifi cally ajoint where a number of tubes forming such a line, are attached to eachother.

In accordance with this invention, it has been found practical toprovide a line consisting of a cascade of tubes which can be connectedduring the installation of the line, but otherwise may be constructed oftubes of such length that can be easily handled during transportation,coating and further assembly.

In a particular realization, a 500 ft. tubular line has been constructedof 25 tubes of 20 ft. length each, consisting of hard drawn copper whichafter having been coated with an appropriate dielectric such aspolyethylene or Teflon (reg. TM), the latter having a loss figure of0.0002; are attached to each other in the field and prior to themounting on the antenna tower. While polyethylene is used as coating,generally, wherc relatively low operating temperatures are permissible,as for example provided for in the fluid system application illustratedin FIG. 1, the application of an electric heating system such asprovided in FIG. 2 would require relatively high tem perature resistantmaterial as a coating such as Teflon.

It has further been found practical, to apply the dielectric coating notby extrusion but by means of heat shrinking of tubular material on thetubes. The tubular material may then consist either of homogenousplastic material such as polyethylene or Teflon of appropriatedielectric constant and low-loss properties as required for surface wavemaintenance.

Alternatively, the heat shrinkable tubing may have a sandwich type ofstructure, and especially in the case of polyethylene, consist of abottom layer of relatively low-loss but weather-sensitive plasticmaterial, and a top layer of relatively high-loss but weatherinsensitive plastic material, whereby the top layer is relatively thincompared to the bottom layer so as to reduce losses to a minimum whilemaintaining a high degree of weather resistivity.

The invention, however, is not limited to any particular dielectricmaterial or coating structure, nor to a particular way of its productionor application.

Nor is the invention limited to any particular way controlling oraffecting the temperature of the tubular line or its dielectricalcoating. In effect, if necessary such systems can be combined, as forexample the fluid system such as exemplified in FIG. 2, with anelectrical heating system such as indicated in FIG. 1, without departingfrom the scope of this disclosure.

Furthermore, since the fluid systems shown in FIG. 1, make the linevirtually independent from the power transmitted therethrough, or theheat produced by such power-which is the case of the above-mentionedexample of a 500 ft. 50 kw., 800 MHz. tubular surface wave transmissionline, may amount to 5 kw.the same line could be used to transmit muchhigher powers as for example in the above-mentioned case, a power of theorder of I00 kw.thereby reducing cost of the design for different powerlines to a minimum.

In FIG. 3 a portion of tubular transmission line is shown incross-sectional view, and more particularly a portion showing a jointbetween two adjacent tubes forming sections of the line and attached toeach other during the installation of the line.

In FIG. 3 the end portions of two line sections consisting for exampleof copper tubes of ft. length, are schematically indicated at 20, 21,respectively, each coated with a dielectric layer in the manner aspreviously indicated, and schematically shown at 22, 23, respectively.Each of copper tubes 20, 21 at each of its ends, is provided with aninsert 24, 25 which may also be of copper or of stainless steel or anyother suitable material. Inserts 24, 25 are provided with outer threadsto permit attachment of tubes 20, 21 to each other with the aid ofintermediate piece 26 which through an inner thread schematicallyindicated at 26', assures electrical and surface contact between tubes20, 21 and, being also coated with a dielectric coating of the typeshown at 22, 23, and indicated for piece 26 at 27, will assure therequired continuity for maintaining a surface wave along the tubularline.

Inserts 24, 25, are attached to the ends of tubes 20, 21 by means of anumber of setscrews schematically indicated in FIG. 3 at 28 which mayalso serve, if necessary, to fix the threads of intermediate pieces 26in their position.

However, inserts 24, 25 may be attached to tubes 20, 21 in any desiredmanner for example by brazing or welding. Alternatively, also withoutdeparting from the scope of this disclosure, the inserts of the typeshown at 24, 25 may be omitted and threads or other attachment elementsdirectly be provided inside and outside, respectively of the adjacentends of tubes 20, 21 in the forms of threads or the like so as to permitassembly in the field to the desired length of transmission line.

If required, further, more intermediate pieces of the type shown at 26may also be omitted and the ends of tubes 20, 21 directly attached toeach other by welding or screwing or in any other way, also withoutdeparting from the scope of this disclosure.

FIG. 3 also shows the attachment of the tubular line, or at least apredetermined portion thereof, to a fluid line to control themaintaining of temperature along the line, in accordance with one of theaspects of the invention, as schematically at 29.

In the modification shown in FIG. 4, designated for applying electricalheating current to an end portion of tubular line 1, such an end portionas indicated in FIG. 4 at 30 is shown connected over a conductor 31 to atemperature controlled source of electric power, not shown but otherwisewell known in the art. In this case, of course, the recirculation pipeshown in FIG. 1 at 12 may be omitted and replaced by a return cable forthe electric heating current, or the tower 2 itself used as an electricreturn medium.

FIG. 5 illustrates a surface wave launcher especially designed tocooperate with a tubular line in accordance with the invention. Thelauncher consists of a transducer schematically indicated at 32including a coaxial line the inner conductor of which is also of tubularshape and dimensions similar to thdse of tubular line 1, asschematically indicated at 33, and also in FIG. 6 in greater detail.

In accordance with one embodiment of the invention, especially where bythe maintaining of constant temperature of operation, which excludeslongitudinal variations of the line, the connection between conductor 33and line 1 is made so as to permit angular deviations, without impairingelectrical contact, fluid transmission and wave propagation. This isachieved by replacing at the exit of transducer 32, the tubularstructure of relative rigid configuration by a flexible phosphore bronzesleeve schematically indicated in FIG. 6 at 34 and attached to innerconductor 33 and line 1, respectively, by screws, rivets or welds.Sleeve 34 can be made flexible by being shaped in the form of a bellow,in the form of phosphore bronze fingers similar to the flexible fingers36 shown in the flexible attachment between transducer 32 and horn 35described further below.

Transducer 32 is connected to a horn which serves in otherwisewell-known manner, to transform the coaxial wave emerging fromtransducer 32 into a surface wave, as indicated in FIG. 5 at 35. Horn 35is also attached flexibly to transducer 32 by means of a number ofphosphore bronze fingers 36, arranged peripherally around the ends ofhorn 35, as shown in greater detail in FIG. 7, where the figures 36 areshown attached to the ends of horn 35 and transducer 32, respectively,in such a way as to permit the born 35 to be supported on the tubularline 1 onlyor its extension inside horn 35-supported thereon ifnecessary by a dielectric cover disc schematically indicated in FIG. 5at 37. In this way, horn 35 is permitted to follow the deviations oftubular line 1 without transferring any strain to transducer 32, and anyequipment connected thereto such as the heavy rigid and mechanicallysensitive coaxial cable connected to the output flange 37 of transducer32.

I claim:

1. In a long-distance high-power antenna feeder system, a continuoustubing which at least at its outer surface is conducting, a dielectriccoating surrounding said conducting surface and adapted to maintain asurface wave of predetermined radius in the space surrounding saidcoating, and means including a circulating fluid connected to the insideof said tubing, and temperature control means adapted to maintain saidfluid at such a constant temperature as to substantially exeludelongitudinal expansions, in a manner substantially independent of thepower level of the surface wave and the temperature surrounding saidtubing.

2. System according to claim 1, comprising a tower, an antenna attachedto its top and a transmitter arranged near its base; wherein said tubingat least partially connects said transmitter and said antenna, andcomprises a series of tubes attached to each other at their ends throughan intermediate tubing adapted to connect adjacent tubes by means ofthreads permitting assembly of the line at the antenna site; each ofsaid tubes having a conducting insert extending from said tube andhaving a thread permitting connection to the thread of said intermediatetubing.

3. System according to claim 2, wherein said tubes consist of copperplated stainless steel.

4. System according to claim 1, wherein said dielectric coating consistsof polyethylene having a dielectric loss figure of the order of 0.0005in the UHF range.

5. System according to claim 1, wherein said dielectric coating consistsof Teflon (trademarked by Dupont) having a dielectric loss figure of theorder of 0.0002 in the UHF range.

6. System according to claim 1, wherein said dielectric coat ingconsists of heat-shrunk material.

7. System according to claim 1, comprising surface wave launcher meansincluding a transducer and a horn flexibly connected to said transducerand supported at least on part of said tubing, and a transmitter rigidlyconnected to said transducer; said transducer including a coaxial linehaving an inner conductor extending therefrom and flexibly connected tosaid tubing so as to permit lateral movements of said tubing only, whilemaintaining said tubing a substantially constant length.

1. In a long-distance high-power antenna feeder system, a continuoustubing which at least at its outer surface is conducting, a dielectriccoating surrounding said conducting surface and adapted to maintain asurface wave of predetermined radius in the space surrounding saidcoating, and means including a circulating fluid connected to the insideof said tubing, and temperature control means adapted to maintain saidfluid at such a constant temperature as to substantially excludelongitudinal expansions, in a manner substantially independent of thepower level of the surface wave and the temperature surrounding saidtubing.
 2. System according to claim 1, comprising a tower, an antennaattached to its top and a transmitter arranged near its base; whereinsaid tubing at least partially connects said transmitter and saidantenna, and comprises a series of tubes attached to each other at theirends through an intermediate tubing adapted to connect adjacent tubes bymeans of threads permitting assembly of the line at the antenna site;each of said tubes having a conducting insert extending from said tubeand having a thread permitting connection to the thread of saidintermediate tubing.
 3. System according to claim 2, wherein said tubesconsist of copper plated stainless steel.
 4. System according to claim1, wherein said dielectric coating consists of polyethylene having adielectric loss figure of the order of 0.0005 in the UHF range. 5.System according to claim 1, wherein said dielectric coating consists ofTeflon (trademarked by Dupont) having a dielectric loss figure of theorder of 0.0002 in the UHF range.
 6. System according to claim 1,wherein said dielectric coating consists of heat-shrunk material. 7.System according to claim 1, comprising surface wave launcher meansincluding a transducer and a horn flexibly connected to said transducerand supported at least on part of said tubing, and a transmitter rigidlyconnected to said transducer; said transducer including a coaxial linehaving an inner conductor extending therefrom and flexibly connected tosaid tubing so as to permit lateral movements of said tubing only, whilemaintaining said tubing a substantially constant length.